1. Field of the Invention
The invention relates to a grinding/polishing machine, and more particularly to a grinding/polishing machine having two coarse and fine grinding units.
2. Description of the Related Art
Referring to FIG. 1, a conventional grinding/polishing machine 1 includes a base support 11, a platform 12 mounted on the machine body 11 and adapted for holding a workpiece 2, a column 13 engaging slidingly the base support 11 along a Y-axis direction, and a grinding unit 14 engaging slidingly the column 13 along a Z-axis direction. The grinding unit 14 has a grinding wheel 141 for grinding the workpiece 2. The grinding wheel 141 is movable relative to the workpiece 2 along the Y-axis direction together with the column 13 and along the Z-axis direction for grinding a surface 21 of the workpiece 2.
The fineness/coarseness of the surface 21 of the workpiece 2 is determined by the grain size of the material of the grinding wheel 141. Generally speaking, when a large amount of grinding is to be performed, a grinding wheel 141 with coarse grains is used to perform a coarse grinding operation. When the surface of the workpiece needs polishing, a grinding wheel 141 with finer grains is used to perform a fine grinding operation.
Since only one grinding wheel 141 can be mounted on the grinding/polishing machine 1, once the grinding wheel 141 is installed on the machine 1, only one mode of grinding operation can be performed. When it is necessary to switch the mode of grinding operation, the existing grinding wheel has to be disassembled from the machine 1, and another grinding wheel has to be re-assembled as a replacement. The task of disassembling and re-assembling the grinding wheel is time consuming, troublesome, and uneconomical.